EP3318063A1 - Procédé et dispositif pour coder à la fois une image hdr et une image sdr obtenue à partir de ladite image hdr à l'aide de fonctions de mappage de couleurs - Google Patents

Procédé et dispositif pour coder à la fois une image hdr et une image sdr obtenue à partir de ladite image hdr à l'aide de fonctions de mappage de couleurs

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Publication number
EP3318063A1
EP3318063A1 EP16775474.6A EP16775474A EP3318063A1 EP 3318063 A1 EP3318063 A1 EP 3318063A1 EP 16775474 A EP16775474 A EP 16775474A EP 3318063 A1 EP3318063 A1 EP 3318063A1
Authority
EP
European Patent Office
Prior art keywords
picture
sdr
color
component
hdr
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP16775474.6A
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German (de)
English (en)
Inventor
Yannick Olivier
Fabrice Leleannec
Patrick Lopez
Philippe Bordes
Sebastien Lasserre
David Touze
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
InterDigital Madison Patent Holdings SAS
Original Assignee
Thomson Licensing SAS
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Publication date
Application filed by Thomson Licensing SAS filed Critical Thomson Licensing SAS
Publication of EP3318063A1 publication Critical patent/EP3318063A1/fr
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/186—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a colour or a chrominance component
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/124—Quantisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/172—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a picture, frame or field
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/182—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a pixel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/44—Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/98—Adaptive-dynamic-range coding [ADRC]

Definitions

  • the present disclosure generally relates to picture/video encoding and decoding.
  • a picture contains one or several arrays of samples (pixel values) in a specific picture/video format which specifies all information relative to the pixel values of a picture (or a video) and all information which may be used by a display and/or any other device to visualize and/or decode a picture (or video) for example.
  • a picture comprises at least one component, in the shape of a first array of samples, usually a luma (or luminance) component, and, possibly, at least one other component, in the shape of at least one other array of samples, usually a color component.
  • the same information may also be represented by a set of arrays of color samples, such as the traditional tri-chromatic RGB representation.
  • a pixel value is represented by a vector of C values, where C is the number of components.
  • Each value of a vector is represented with a number of bits which defines a maximal dynamic range of the pixel values.
  • Standard-Dynamic-Range pictures are color pictures whose luminance values are represented with a limited dynamic usually measured in power of two or f-stops.
  • SDR pictures have a dynamic range, also called a dynamic in the following, around 10 f-stops, i.e. a ratio 1000 between the brightest pixels and the darkest pixels in the linear domain, and are coded with a limited number of bits (most often 8 or 10 in HDTV (High Definition Television systems) and UHDTV (Ultra-High Definition Television systems) in a non-linear domain, for instance by using the ITU-R BT.709 OETF (Optico-Electrical-Transfer-Function) ⁇ Rec.
  • ITU-R BT.709 OETF Optico-Electrical-Transfer-Function
  • ITU-R BT 709-5, April 2002 or ITU-R BT.2020 OETF (Rec. ITU-R BT.2020-1, June 2014) to reduce the dynamic.
  • This limited non-linear representation does not allow correct rendering of small signal variations, in particular in dark and bright luminance ranges.
  • High-Dynamic-Range pictures the signal dynamic is much higher (up to 20 f-stops, a ratio one million between the brightest pixels and the darkest pixels) and a new non-linear representation is needed in order to maintain a high accuracy of the signal over its entire range.
  • raw data are usually represented in floating-point format (either 32-bit or 16-bit for each component, namely float or half-float), the most popular format being openEXR half-float format (16-bit per RGB component, i.e. 48 bits per pixel) or in integers with a long representation, typically at least 16 bits.
  • floating-point format either 32-bit or 16-bit for each component, namely float or half-float
  • openEXR half-float format (16-bit per RGB component, i.e. 48 bits per pixel
  • integers with a long representation typically at least 16 bits.
  • a color gamut is a certain complete set of colors. The most common usage refers to a set of colors which can be accurately represented in a given circumstance, such as within a given color space or by a certain output device.
  • a color gamut is sometimes defined by RGB primaries provided in the CIE1931 color space chromaticity diagram and a white point as illustrated in Fig. 1.
  • a gamut is defined in this diagram by the triangle whose vertices are the set of (x,y) coordinates of the three primaries RGB.
  • the white point W is another given (x,y) point belonging to the triangle, usually close to the triangle center.
  • a color volume is defined by a color space and a dynamic range of the values represented in said color space.
  • a color gamut is defined by a RGB ITU-R Recommendation BT.2020 color space for UHDTV.
  • An older standard, ITU-R Recommendation BT.709 defines a smaller color gamut for HDTV.
  • the dynamic range is defined officially up to 100 nits (candela per square meter) for the color volume in which data are coded, although some display technologies may show brighter pixels.
  • a change of gamut i.e. a transform that maps the three primaries and the white point from a gamut to another, can be performed by using a 3x3 matrix in the linear RGB color space.
  • a change of space from XYZ to RGB is performed by a 3x3 matrix.
  • a change of gamut can be performed by a 3x3 matrix.
  • a gamut change from BT.2020 linear RGB to BT.709 XYZ can be performed by a 3x3 matrix.
  • High Dynamic Range pictures are color pictures whose luminance values are represented with a HDR dynamic that is higher than the dynamic of a SDR picture.
  • the HDR dynamic is not yet defined by a standard but one may expect a dynamic range up to a few thousands nits.
  • a HDR color volume is defined by a RGB BT.2020 color space and the values represented in said RGB color space belong to a dynamic range from 0 to 4000 nits.
  • Another example of HDR color volume is defined by a RGB BT.2020 color space and the values represented in said RGB color space belong to a dynamic range from 0 to 1000 nits.
  • Color-grading a picture is a process of altering/enhancing the colors of the picture (or the video).
  • color-grading a picture involves a change of the color volume (color space and/or dynamic range) or a change of the color gamut relative to this picture.
  • two different color- graded versions of a same picture are versions of this picture whose values are represented in different color volumes (or color gamut) or versions of the picture whose at least one of their colors has been altered/enhanced according to different color grades. This may involve user interactions.
  • RGB color values composed of 3 components (Red, Green and Blue).
  • the RGB color values depend on the trichromatic characteristics (color primaries) of the sensor.
  • a HDR color-graded version of the captured picture (or video) is then obtained in order to get theatrical renders (using a specific theatrical grade).
  • the values of the first color-graded version of the captured picture (or video) are represented according to a standardized YUV format such as BT.2020 which defines parameter values for UHDTV.
  • the YUV format is typically performed by applying a non-linear function, so called Optical Electronic Transfer Function (OETF) on the linear RGB components to obtain non-linear components R'G'B', and then applying a color transform (usually a 3x3 matrix) on the obtained non-linear R'G'B' components to obtain the three components YUV.
  • OETF Optical Electronic Transfer Function
  • the first component Y is a luminance component and the two components U,V are chrominance components.
  • a Colorist usually in conjunction with a Director of Photography, performs a control on the color values of the first color-graded version of the captured picture (or video) by fine-tuning/tweaking some color values in order to instill an artistic intent.
  • a SDR color-graded version of the captured picture is also obtained to get home release renders (using specific home, Blu-Ray Disk/DVD grade).
  • the values of the second color-graded version of the captured picture are represented according to a standardized YUV format such as ITU-R Recommendation BT.601 (Rec. 601 ) which defines studio encoding parameters of Standard Digital Television for standard 4:3 and wide-screen 16:9 aspect ratios, or ITU-R Recommendation BT.709 which defines parameter values for High Definition Television systems (HDTV).
  • Obtaining such a SDR color-graded version of the captured picture usually comprises shrinking the color volume of the first color-graded version of the captured picture (for example RGB BT.2020 1000 nits modified by the Colorist) in order that the second color-graded version of the captured picture belong to a second color volume (RGB BT.709 1000 nits for example).
  • This is an automatic step which uses a color mapping function (CMF) (for example for mapping of RGB BT.2020 format to RGB BT.709) usually approximated by a three dimensional look-up-table (also called 3D LUT).
  • CMF color mapping function
  • RGB BT.2020 format for example for mapping of RGB BT.2020 format to RGB BT.709
  • 3D LUT three dimensional look-up-table
  • a Colorist usually in conjunction with a Director of Photography, performs a control on the color values of the second color-graded version of the captured picture by fine-tuning/tweaking some color values in order to instill the artistic intent in the home release.
  • the problem to be solved is the distribution of both the HDR color- graded version and the SDR color-graded version of the captured picture (or video), i.e. the distribution of a compressed HDR picture (or video) representative of a color-graded version of a captured picture (or video) while, at the same time, distributing an associated SDR picture (or video) representative of a color-graded SDR version of said captured picture (or video) for backward compatibility with legacy SDR displays for example.
  • Said associated SDR picture (or video) is sometimes called an imposed SDR picture (video).
  • a straightforward solution is simulcasting both these HDR and SDR color graded pictures (or videos) on a distribution infrastructure.
  • the drawback of this solution is to virtually double the needed bandwidth compared to a legacy infrastructure adapted to broadcast a SDR picture (or video) such as HEVC main 10 profile ("High Efficiency Video Coding", SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS, Recommendation ITU-T H.265, Telecommunication Standardization Sector of ITU, October 2014).
  • Using a legacy distribution infrastructure is a requirement to accelerate the emergence of the distribution of HDR pictures (or video). Also, the bitrate shall be minimized while ensuring good quality of both the HDR and SDR pictures (or videos).
  • the present principles set out to remedy at least one of the drawbacks of the prior art with a method of encoding both a HDR picture and a first SDR picture obtained from said HDR picture, in at least one bitstream, the method comprising:
  • - obtaining two chrominance components by: - obtaining at least one intermediate color component by scaling each color component by a factor that depends on the luminance component;
  • the second HDR picture is obtained by combining together the luminance component and the two chrominance components.
  • SDR pictures are the first SDR picture.
  • the fourth SDR picture is the first SDR picture and the third SDR picture is a decoded version of the encoded first SDR picture.
  • the third SDR picture is the first SDR picture and the fourth SDR picture is obtained by applying the color mapping function onto the colors of the second SDR picture.
  • the third SDR picture is a decoded version of the encoded first SDR picture and the fourth SDR picture is obtained by applying the color mapping function onto the colors of the second SDR picture.
  • the present principles relate to a method of decoding a HDR picture from at least one bitstream comprising:
  • the decoded picture is obtained by combining together said at least one color component.
  • the present principles relate to a device of encoding both a HDR picture and a first SDR picture obtained from said HDR picture, in at least one bitstream, characterized in that the device comprises a processor configured to:
  • the second HDR picture is obtained by combining together the luminance component and the two chrominance components
  • the present principles relate to a device of decoding a HDR picture from at least one bitstream, characterized in that the device comprises a processor configured to:
  • the decoded picture is obtained by combining together said at least one color component.
  • the present principles relate to a device comprising a processor configured to implement the above method, a computer program product comprising program code instructions to execute the steps of the above method when this program is executed on a computer, a processor readable medium having stored therein instructions for causing a processor to perform at least the steps of the above method, and a non- transitory storage medium carrying instructions of program code for executing steps of the above method when said program is executed on a computing device.
  • - Fig. 1 shows examples of CIE1931 color space chromaticity diagram
  • FIG. 2 shows a block diagram of the steps of a method for encoding both a HDR picture and a SDR picture in accordance with the present principles
  • FIG. 3 shows a diagram of the steps of a method for decoding a HDR picture IHDR and a SDR picture ISDRI in accordance with an example of the present principles
  • Fig. 4 shows a diagram of the steps of an example of the method for encoding both the HDR picture IHDR and the first SDR picture ISDRI as described in relation with Fig. 2;
  • Fig. 5 shows a diagram of the steps of a method for encoding both a HDR picture and a SDR picture in accordance with a variant of Fig. 4.
  • - Fig. 6 shows a diagram of the steps of an example of the method for encoding both the HDR picture IHDR and the first SDR picture ISDRI as described in relation with Fig. 2;
  • - Fig. 7 shows a diagram of the steps of a method for encoding both a HDR picture and a SDR picture in accordance with a variant of Fig. 6;
  • FIG. 8a-d show diagrams of the sub-steps of the step 210 in accordance with examples of the present principles
  • Fig. 9 shows a diagram of the steps of a method for decoding both a
  • HDR picture and a SDR picture in accordance with an example of the present principles.
  • FIG. 10a-c show diagrams of the sub-steps of the step 210 in accordance with examples of the present principles
  • FIG. 11a-d show diagrams of the steps of a method of decoding a
  • FIG. 12 shows an example of an architecture of a device in accordance with an example of present principles
  • FIG. 13 shows two remote devices communicating over a communication network in accordance with an example of present principles
  • each block represents a circuit element, module, or portion of code which comprises one or more executable instructions for implementing the specified logical function(s).
  • the function(s) noted in the blocks may occur out of the order noted. For example, two blocks shown in succession may, in fact, be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending on the functionality involved.
  • references herein to " an example”, “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment or an example can be included in at least one implementation of the disclosure.
  • the appearances of the phrase “in one embodiment”, “according to an embodiment” “in one example” or “ in accordance with an example” in various places in the specification are not necessarily all referring to the same embodiment or example, nor are separate or alternative embodiments or examples necessarily mutually exclusive of other embodiments or examples.
  • the present principles is described for encoding/decoding a picture but extends to the encoding/decoding of a sequence of pictures (video) because each picture of the sequence is sequentially encoded/decoded as described below.
  • Fig. 2 shows a diagram of the steps of a method for encoding both a HDR picture IHDR and a SDR picture ISDRI in accordance with the present principles.
  • the HDR picture IHDR is a color-graded version of a captured picture (or video) according to a first grade
  • the first SDR picture ISDRI is a color- graded version of said captured picture (or video) according to a second grade as explained above.
  • the constraint on this encoding method is that the color-grade of the SDR picture ISDRI shall be rendered at the decoder or at least a SDR picture having a visual content very close to the visual content of SDR picture ISDRI in order to preserve the artist intent.
  • a module TM obtains a second SDR picture ISDR2 by tone- mapping the HDR picture IHDR.
  • tone-mapping means any approach that reduces the dynamic range of the HDR picture IHDR to a targeted dynamic range. Examples of tone-mapping approaches are given in Fig. 8a-d, 9, 10a-d but the present disclosure is not limited to a specific tone-mapping approach.
  • a module SDR1 -to-SDR3 obtains a third SDR picture ISDR3 from the first SDR picture ISDRL
  • a module CM obtains a color mapping function CMF that allows the mapping of the colors of the second SDR picture ISDR2 onto the colors of the third SDR picture ISDR3 in order to minimize the differences between the second SDR picture lsDR2 and the third SDR picture ISDR3.
  • the color mapping function is obtained by minimizing a mean square error calculated by subtracting the pixel values of the third SDR picture ISDR3 from the pixels of the SDR picture ISDR2.
  • An example of color mapping function is given by the standard HEVC with color remapping information SEI message (Annex. D.2.32).
  • the present disclosure is not limited to a specific color mapping function but extend to any kind of mapping function.
  • an encoder ENC1 encodes, in a bitstream F1 , an information INF representative of the color mapping function CMF.
  • the information INF is an index allowing to retrieve the color mapping function CMF from a list of color mapping functions.
  • the information INF represent parameters of the color mapping function CMF.
  • a module SDR1 -to-SDR4 obtains a fourth SDR picture ISDR4 from the first SDR picture ISDRL
  • an encoder ENC2 encodes the fourth SDR picture ISDR4 in a bitstream F2.
  • Fig. 3 shows a diagram of the steps of a method for decoding a HDR picture IHDR and a SDR picture ISDRI in accordance with an example of the present principles.
  • a decoder DEC2 obtains a decoded SDR picture, called a decoded fourth SDR picture ISDR4, by decoding a bitstream F2.
  • a module SDR4-to-SDR1 obtains a decoded first SDR picture ISDRI from the decoded fourth SDR picture ISDR4.
  • step 220 the module SDR1 -to-SDR3 obtains a decoded third SDR picture ISDR3 from the decoded first SDR picture ISDRI .
  • a decoder DEC1 obtains an information INF representative of a color mapping function CMF by decoding at least partially a bitstream F1 .
  • the information INF is representative of the inverse of the color mapping function CMF.
  • a module AP _1 obtains a decoded second SDR picture
  • a module ITM obtains a decoded HDR picture IHDR by applying an inverse-tone-mapping to the decoded second SDR picture ISDR2.
  • the inverse-tone-mapping is the inverse of the tone-mapping used in step 210 in Fig. 2.
  • Fig. 4 shows a diagram of the steps of an example of the method for encoding both the HDR picture IHDR and the first SDR picture ISDRI as described in relation with Fig. 2.
  • the modules SDR1 -to-SDR3 and SDR1 -to-SDR4 are configured in order that the SDR pictures ISDR3 and ISDR4 equal the SDR picture ISDRI .
  • step 230 the color mapping function CMF is then obtained to allow the mapping of the colors of the second SDR picture ISDR2 onto the colors of the first SDR picture ISDRI, and in step 260, the first SDR picture ISDRI is directly encoded by the encoder ENC2.
  • the first SDR picture ISDRI as color-graded by the colorist is thus directly available by decoding the bitstream F2. The artist intent is thus preserved when the decoded first SDR picture ISDRI is displayed.
  • Fig. 5 shows a diagram of the steps of a method for encoding both a
  • the module SDR1 -to-SDR4 is configured in order that the fourth SDR picture ISDR4 is the first SDR picture ISDRI
  • the first SDR picture ISDRI as color- graded by the colorist, is thus directly available by decoding the bitstream F2. The artist intent is thus preserved when the decoded first picture ISDRI is displayed.
  • the module SDR1 -to-SDR3 is configured to encode the first SDR picture ISDRI by using the encoder ENC2, and to obtain the third SDR picture ISDR3 by decoding the encoded first SDR picture ISDRI according to a decoder DEC2 (step 310).
  • step 230 the color mapping function CMF is then obtained to allow the mapping of the colors of the SDR picture ISDR2 onto the colors of the decoded version of the encoded first SDR picture ISDRI .
  • Determining the color mapping function CMF from the decoded version of the encoded first SDR picture ISDRI rather than from the first SDR picture ISDRI leads to a decoded second SDR picture ISDR2 (obtained at the decoding side) whose the content is closer to the content of the second SDR picture ISDR2 used at the encoding side. Then, the decoded HDR picture, obtained from the decoded second SDR picture ISDR2 and the color mapping function determined from said decoded second SDR picture ISDR2, at the encoding side, has a visual content closer to the visual content of the original HDR picture, improving the performance of the HDR encoding/decoding scheme of Fig. 4.
  • Fig. 6 shows a diagram of the steps of an example of the method for encoding both the HDR picture IHDR and the first SDR picture ISDRI as described in relation with Fig. 2;
  • the module SDR1 -to-SDR3 is configured in order that the SDR pictures ISDR3 is the SDR picture ISDRI .
  • step 230 the color mapping function CMF is then obtained to allow the mapping of the colors of the second SDR picture ISDR2 onto the colors of a first SDR picture ISDRI .
  • the module SDR1 -to-SDR4 comprises a module AP (step 610) to obtain the fourth SDR picture ISDR4 by applying the color mapping function CMF (obtained from the SDR picture ISDRI) onto the colors of the second SDR picture ISDR2.
  • the content of the fourth SDR picture ISDR4 is thus close to the content of the first SDR picture ISDRI because the color mapping function CMF is determined in order to minimize the differences between these two pictures.
  • Fig. 7 shows a diagram of the steps of a method for encoding both a HDR picture IHDR and a SDR picture ISDRI in accordance with a variant of Fig. 6.
  • the module SDR1 -to-SDR3 is configured to encode (step 260) the first SDR picture ISDRI by using the encoder ENC2, and to obtain the third SDR picture ISDR3 by decoding the encoded first SDR picture ISDRI according to the decoder DEC2 (step 310).
  • Determining the color mapping function CMF from the decoded version of the encoded first SDR picture ISDRI rather than from the first SDR picture ISDRI leads to a decoded second SDR picture ISDR2 (obtained at the decoding side) whose the content is closer to the content of the second SDR picture ISDR2 used at the encoding side. Then, the decoded HDR picture, obtained from the decoded second SDR picture ISDR2 and the color mapping function determined from said decoded second SDR picture ISDR2, at the encoding side, has a visual content closer to the visual content of the original HDR picture, improving the performance of the HDR encoding/decoding scheme of Fig. 6.
  • the module TM applies a tone-mapping operator onto the HDR picture IHDR in order to reduce the dynamic range of the luminance of the HDR picture IHDR to a target dynamic range.
  • the invention is not limited to any specific tone-mapping operator. This single condition is that the tone-mapping operator shall be reversible.
  • the tone-mapping operator defined by Reinhard may be used (Reinhard, E., Stark, M., Shirley, P., and Ferwerda, J., ⁇ Photographic tone reproduction for digital images, " ACM Transactions on Graphics 21 (July 2002)), or defined by Boitard, R., Bouatouch, K., Cozot, R., Thoreau, D., & Gruson, A. (2012). Temporal coherency for video tone mapping. In A. M. J. van Eijk, C. C. Davis, S. M. Hammel, & A. K. Majumdar (Eds.), Proc. SPIE 8499, Applications of Digital Image Processing (p. 84990D-84990D-10)).
  • Fig. 8a-d show diagrams of the sub-steps of the step 210 in accordance with examples of the present principles.
  • the module TM comprises a module BAM configured to obtain a backlight picture Ba from the HDR picture IHDR (step 2101 ).
  • the module BAM comprises a module Bl which obtains the backlight picture Ba from the luminance component L of the HDR picture IHDR.
  • the luminance component L is obtained, for instance in the 709 color gamut, by a linear combination which is given by:
  • the backlight picture Ba is determined as being a weighted linear combination of shape functions given by:
  • determining a backlight picture Ba from a luminance component L consists in finding optimal weighting coefficients (and potentially also optimal shape functions if not known beforehand) in order that the backlight picture Ba fits the luminance component L.
  • optimal weighting coefficients and potentially also optimal shape functions if not known beforehand
  • shape functions may be the true physical response of a display backlight (made of LED's for instance, each shape function then corresponding to the response of one LED) or may be a pure mathematical construction in order to fit the luminance component at best.
  • the module BAM further comprises a module BM which modulate the backlight picture Ba (given by equation (1 )) with a mean luminance value L mean of the HDR picture IHDR obtained by the means of a module HL.
  • the module HL is configured to calculate the mean luminance value L mean over the whole luminance component L.
  • the module HL is configured to calculate the mean luminance value L mean by
  • This last example is advantageous because it avoids that the mean luminance value L mean be influenced by a few pixels with extreme high values which usually leads to very annoying temporal mean brightness instability when the HDR picture IHDR belongs to a sequence of images.
  • the invention is not limited to a specific embodiment for calculating the mean luminance value L mean .
  • a module N normalizes the backlight image Ba (given by equation (1 )) by its mean value E(Ba) such that one gets a backlight picture Ba gray (having a mid-grey equals to 1 ) for the HDR picture (or for all HDR pictures if the HDR picture belongs to a sequence or group of pictures):
  • the module BM is configured to modulate the backlight picture
  • cst mod being a modulation coefficient and a being another modulation coefficient less than 1 , typically 1/3.
  • cstmod * 1 .7 for a backlight picture is obtained by least means squares.
  • the present disclosure is not limited to any way to obtain a backlight picture Ba from the HDR picture IHDR.
  • step 2102 in Fig. 8a, the second SDR picture ISDR2 is obtained by dividing, pixel by pixel, the HDR picture IHDR by the backlight picture Ba.
  • an encoder ENC3 encodes the backlight picture Ba in a bitstream F3.
  • Dividing the HDR picture IHDR by the backlight picture Ba reduces the dynamic range of the HDR picture.
  • a method as described in relation with Fig. 8a-d may thus be considered as being a tone-mapping of the HDR picture IHDR.
  • Fig. 9 shows a diagram of the steps of a method for decoding both a HDR picture and a SDR picture in accordance with an example of the present principles.
  • This example allows getting both a HDR picture and a SDR picture when those pictures have been previously encoded by a method as described in relation with Figs. 8a-d.
  • the module ITM in step 350, comprises a decoder DEC3 which obtains a decoded backlight picture Ba by decoding a bitstream F3 (step 3501 ).
  • the decoded HDR picture IHDR is obtained by multiplying the second SDR picture ISDR2 by the decoded backlight picture Ba. Multiplying the second SDR picture ISDR2 by the decoded backlight picture Ba increases the dynamic range of the resulting HDR picture compared to the second SDR picture ISDR2, i.e such multiplyinig may be considered as being inverse-tone-mapping.
  • Fig. 10a-c show diagrams of the sub-steps of the step 210 in accordance with examples of the present principles.
  • the present disclosure is not limited to any color space in which the three components Ec are represented but extends to any color space such as RGB, CIELUV, XYZ, CIELab, etc.
  • a luminance component L and two chrominance components C1 and C2 are determined from the three color components Ec of the HDR picture IHDR.
  • the luminance and chrominance components form a SDR color picture whose pixel values are represented in the color space (L, C1 , C2).
  • Said SDR color picture is viewable by a legacy SDR display, i.e. has a sufficient visual quality in order to be viewed by a legacy SDR display.
  • a module IC obtains a component Y that represents the luminance of the HDR picture IHDR by linearly combining together the three components Ec:
  • A1 is the first row of a 3x3 matrix A that defines a color space transforms from the (E1 , E2, E3) color space to a color space (Y, C1 , C2).
  • a module BMM obtains a module value Bm from the component Y.
  • the modulation value Bm is an average, median, min or max value of the pixel values of the component Y.
  • These operations may be performed in the linear HDR luminance domain Yin or in a non-linear domain like ln(Y) or Y Y with ⁇ 1 .
  • a module FM obtains the luminance component L by applying a non-linear function f on the component Y:
  • the dynamic range of the component Y is reduced in order that the luminance values of the component L are represented by using 10 bits.
  • the component Y is divided by the modulation value Bm before applying the non-linear function f:
  • the non-linear function f is a gamma function:
  • Y 1 equals either Y or Y/Ba according to the embodiments of eq. (3) or (4), B is a constant value, y is a parameter (real value strictly below 1 ).
  • the non-linear function f is a S-Log function:
  • a, b and c are parameters (real values) of a SLog curve determined such that f(0) and f(1 ) are invariant, and the derivative of the SLog curve is continuous in 1 when prolonged by a gamma curve below 1 .
  • a, b and c are functions of the parameter y. Typical values are shown in Table 1 .
  • a value of ⁇ close to 1/2.5 is efficient in terms of HDR compression performance as well as good viewability of the obtained SDR luma.
  • the non-linear function f is either a gamma correction or a SLog correction according to the pixel values of the component Y.
  • the module FM applies either the gamma correction or the SLog correction according to the pixel values of the component Y.
  • An information data Inf may indicate whether either the gamma correction or Slog correction applies.
  • the gamma correction is applied and otherwise the SLog correction is applied.
  • a modulation value Bm is determined for every HDR picture, a Group of Pictures (GOP) or for a part of a HDR picture such as, but not limited to, a slice or a Transfer Unit as defined in HEVC.
  • GOP Group of Pictures
  • the value Bm and/or the parameters of the non-linear function f (such as a, b, c or y) and/or the information data Inf is (are) stored in a local or remote memory and/or added into a bitstream F3.
  • a color component Ec may be obtained directly from a local or a remote memory or by applying a color transform on the HDR picture IHDR.
  • r(L(i)) is a factor (real value), determined by the module RM (step 150a), that depends on the value of a pixel i of the component L, E c ' (i) is the value of the pixel i of the intermediate color component E'c, and E c (i) is the value of the pixel i of the color component Ec.
  • Scaling by a factor means multiplying by said factor or dividing by the inverse of said factor.
  • the factor r(L) is the ratio of the luminance component L over the component Y:
  • Y(i) being the value of a pixel i of the component Y.
  • the value Y(i) of a pixel of the component Y depends non-ambiguously on the value L(i) of a pixel of the luminance component L, such that the ratio can be written as a function of L(i) only.
  • This example is advantageous because scaling each color component Ec by the factor r(L) that further depends on the component Y preserves the hue of the colors of the HDR picture IHDR and thus improves the visual quality of the decoded color picture.
  • colorfulness, chroma, and saturation refer to the perceived intensity of a specific color.
  • Colorfulness is the degree of difference between a color and gray.
  • Chroma is the colorfulness relative to the brightness of another color that appears white under similar viewing conditions.
  • Saturation is the colorfulness of a color relative to its own brightness.
  • a highly colorful stimulus is vivid and intense, while a less colorful stimulus appears more muted, closer to gray.
  • a color is a "neutral" gray (a picture with no colorfulness in any of its colors is called grayscale). Any color can be described from its colorfulness (or chroma or saturation), lightness (or brightness), and hue. The definition of the hue and saturation of the color depends on the color space used to represent said color.
  • the saturation s uv is defined as the ratio between the chroma C * over the luminance L * .
  • the saturation is defined as the ratio of the chroma over the luminance:
  • the colors of the second SDR picture ISDR2 are thus differently perceived by a human being because the saturation and the hue of the colors changed.
  • the factor r(L) is given by:
  • This last embodiment is advantageous because it prevents the factor from going to zero for very dark pixels, i.e. allows the ratio to be invertible regardless of the pixel value.
  • step 160a the two chrominance components C1 , C2 are obtained from said at least one intermediate color components E'c.
  • the OETF is defined by the ITU-R recommendation BT.709 or BT.2020 and stated as follows
  • This variant is advantageous because it provides a good approximation of the OETF defined by the ITU-R recommendation BT.709 or BT.2020 and leads to a low complexity decoder.
  • This variant is advantageous because it provides a good approximation of the OETF defined by the ITU-R recommendation BT.709 or BT.2020 but it leads to a somewhat more complex decoder than the decoder obtains when the OETF is approximated by a square-root.
  • a module LC1 obtains the two chrominance components C1 and C2 by linearly combining the three intermediate components Dc:
  • a module COM obtains the second SDR picture ISDR2 by combining together the luminance component L and the chrominance components C1 and C2.
  • Fig. 11a-d show diagrams of the steps of a method of decoding a HDR picture and a SDR picture from at least one bitstream in accordance with an example of the present principles.
  • a module DECOMB obtains a luminance component L and two chrominance components C1 , C2 from the second SDR picture
  • a module IFM obtains a first component Y by applying a non-linear function f 1 on the luminance component L in order that the dynamic of the first component Y is increased compared to the dynamic of the luminance component L:
  • the non-linear function f 1 is the inverse of the non-linear function f (step 1 10a).
  • the examples of the function f 1 are defined according to the examples of the function f.
  • the value Bm and/or the parameters of the non-linear function f 1 (such as a, b, c or 7) and/or the information data Inf is (are) obtained from a local or remote memory (for example a Look-Up-Table) and/or from a bitstream F3 as illustrated in Fig. 11a.
  • the luminance component L is multiplied by the modulation value Bm after having applied the non-linear function f _1 :
  • the non-linear function f 1 is the inverse of a gamma function.
  • Y 1 equals Y or Y/Bm according to the embodiments of eq. (5) or (6)
  • B is a constant value
  • y is a parameter (real value strictly below 1 ).
  • the non-linear function f 1 is the inverse of a S-Log function.
  • the non-linear function f is the inverse of either a gamma correction or a SLog correction according to the pixel values of the component Y. This is indicated by the information data Inf.
  • a module ILC obtains at least one color component Ec from the first component Y, the two chrominance component C1 , C2, and from a factor r(L) that depends on the luminance component L.
  • the decoded HDR picture IHDR is then obtained by combining together said at least one color component Ec.
  • the factor r(L) may be obtained either from a local or remote memory (such a Look-Up-Table) or from a bitstream .
  • the intermediate components Dc are related to the component Y, the two chrominance components C1 , C2 and the factor r(L):
  • EOTF Electro-Optical Trans Function
  • Equation (7b) provides
  • equation (10) may be solved numerically by using the so-called Newton's method or any other numerical method to find the root of a regular function.
  • a module ILEC obtains three intermediate color component E'c from the first component Y, the two chrominance component C1 , C2 and the factor r(L) as above explained.
  • the three color components Ec are obtained by scaling each intermediate color component E'c by the factor r(L):
  • r(L(i)) is the factor given by step 150a that depends on the value of a pixel i of the component L (output of step 111 a)
  • E c ' (i) is the value of the pixel i of an intermediate color component E'c
  • E c (i) is the value of the pixel i of the color component Ec.
  • step 1121 a before step 1122a is the inverse of the order step 161 b followed by step 162b of the encoding method (Fig. 10b).
  • the OEFT is a square root function and the EOTF is then a square function.
  • the OEFT is a cubic root function and the EOTF is then a cubic function.
  • the component Y and the color components Ec are related by: where Fc are components equal to OETF(Ec) and /OETF(r(L))
  • step 1 121 c When the OETF fulfills the commutation conditions, according to a second example of the step 1 12a, illustrated in Fig. 11 c, in step 1 121 c, two intermediate components C'1 and C'2 are obtained by scaling the two chrominance components C1 and C2 by the factor OEFT(r(L(i))) where OETF is the function used in step 161 b in Fig. 10b:
  • r(L(i)) is the factor given by step 150a that depends on the value of a pixel i of the component L (output of step 1 1 1 a), C ⁇ i), C 2 (i) is respectively the value of the pixel i of the component C'1 and C'2, C 1 (i), C 2 (i) is respectively the value of the pixel i of the component C1 and C2.
  • a module ILEC obtains the three color components Ec from the first component Y and the two intermediate chrominance components C'1 , C'2 as above explained.
  • the OEFT is a square root function and the EOTF is then a square function. Then, in step 1 122c, the two intermediate components C'1 and C'2 are obtained by scaling the two chrominance components C1 and C2 by the factor A /r(L(i))
  • Equation(1 1 ) becomes
  • Equation (14) becomes:
  • Equation (17) is a second order equation that may be solved analytically.
  • This analytic solution leads to a specific embodiment of the step 1 122c as illustrated in Fig. 11 d.
  • This embodiment is advantageous because it allows an analytic expression of the EOTF (inverse of the OETF), and thus of the decoded components of the HDR picture. Moreover, the EOTF is then the square function that is a low complexity process at the decoding side.
  • a module SM obtains a second component S by combining together the two intermediate chrominance components C'1 , C'2 and the first component
  • a module LC2 obtains the three solver components Fc by linearly combining together the intermediate chrominance component C'1 , C'2 and a second component S:
  • C is a 3x3 matrix defined as the inverse of the matrix A.
  • step 1 1223c the three color components Ec are obtained by taking the square of each intermediate color components (Dc):
  • the matrix A determines the transform of the HDR picture IHDR to be encoded from the color space (E1 , E2, E3), in which the pixel values of the HDR picture to be encoded are represented, to the color space (Y, C1 , C2).
  • Such a matrix depends on the gamut of the HDR picture IHDR to be encoded.
  • the matrix A is given by:
  • the OETF is a cubic root function and the EOTF is then a cubic function.
  • the two intermediate components C'1 and C'2 may then be obtained by scaling the two chrominance components C1 and C2 by the factor 3 7r(L(i):
  • the decoder DEC1 (respectively DEC2, DEC3) is configured to decode data which have been encoded by the encoder ENC1 (respectively ENC2, ENC3).
  • the encoder ENC1 and/or ENC2 and/or ENC3 (and decoder DEC1 and/or DEC2 and/or DEC3) may be block-based processing.
  • the encoders ENC1 and/or ENC2 and/or ENC3 (and decoder DEC1 and/or DEC2 and/or DEC3) is not limited to a specific encoder (decoder).
  • the encoder ENC1 is configured to encode the information INF in a SEI message such as the color remapping information SEI message as defined in the HEVC standard (Annex D.2.32).
  • the encoder ENC3 is configured to encode the backlight picture Ba as an auxiliary picture or by using frame packing (Annex D.2.16) as described in the HEVC standard, or to encode the weighting coefficients and possibly the shape functions in a SEI message (HEVC standard, Annex D1 ).
  • the decoder DEC3 is configured to ...the decoded backlight picture Ba obtained from an auxiliary picture or a packed frame encoded in the bitstream F1 as described in the HEVC standard, or is obtained from weighting coefficients and possibly shape functions obtained from a SEI message in the bitstream F1 .
  • the encoder ENC1 and/or ENC2 (and decoder DEC1 and/or DEC2) is not limited to a specific encoder which may be, for example, an image/video coder with loss like JPEG, JPEG2000, MPEG2, HEVC recommendation or H264/AVC recommendation ("Advanced video coding for generic audiovisual Services", SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS, Recommendation ITU-T H.264, Telecommunication Standardization Sector of ITU, February 2014)).
  • the bitstreams F1 , F2, F3 may be multiplexed together to form a single bitstream.
  • the modules are functional units, which may or not be in relation with distinguishable physical units. For example, these modules or some of them may be brought together in a unique component or circuit, or contribute to functionalities of a software. A contrario, some modules may potentially be composed of separate physical entities.
  • the apparatus which are compatible with the disclosure are implemented using either pure hardware, for example using dedicated hardware such ASIC or FPGA or VLSI, respectively « Application Specific Integrated Circuit » « Field- Programmable Gate Array » « Very Large Scale Integration » or from several integrated electronic components embedded in a device or from a blend of hardware and software components.
  • Fig. 12 represents an exemplary architecture of a device 1200 which may be configured to implement a method described in relation with Fig. 1 - 11d.
  • Device 1200 comprises following elements that are linked together by a data and address bus 1201 :
  • microprocessor 1202 which is, for example, a DSP (or Digital Signal Processor);
  • ROM Read Only Memory
  • RAM or Random Access Memory
  • the battery 1206 is external to the device.
  • the word « register » used in the specification can correspond to area of small capacity (some bits) or to very large area (e.g. a whole program or large amount of received or decoded data).
  • the ROM 1203 comprises at least a program and parameters.
  • the ROM 1203 may store algorithms and instructions to perform techniques in accordance with present principles.
  • the CPU 1202 uploads the program in the RAM and executes the corresponding instructions.
  • RAM 1204 comprises, in a register, the program executed by the CPU 1202 and uploaded after switch on of the device 1200, input data in a register, intermediate data in different states of the method in a register, and other variables used for the execution of the method in a register.
  • the implementations described herein may be implemented in, for example, a method or a process, an apparatus, a software program, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method or a device), the implementation of features discussed may also be implemented in other forms (for example a program).
  • An apparatus may be implemented in, for example, appropriate hardware, software, and firmware.
  • the methods may be implemented in, for example, an apparatus such as, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as, for example, computers, cell phones, portable/personal digital assistants ("PDAs”), and other devices that facilitate communication of information between end-users.
  • PDAs portable/personal digital assistants
  • the HDR or SDR picture is obtained from a source.
  • the source belongs to a set comprising:
  • a local memory e.g. a video memory or a RAM (or Random Access Memory), a flash memory, a ROM (or Read Only Memory
  • a storage interface (1205) e.g. an interface with a mass storage, a RAM, a flash memory, a ROM, an optical disc or a magnetic support;
  • a communication interface (1205) e.g. a wireline interface (for example a bus interface, a wide area network interface, a local area network interface) or a wireless interface (such as a IEEE 802.1 1 interface or a Bluetooth® interface); and
  • a wireline interface for example a bus interface, a wide area network interface, a local area network interface
  • a wireless interface such as a IEEE 802.1 1 interface or a Bluetooth® interface
  • an picture capturing circuit e.g. a sensor such as, for example, a CCD (or Charge-Coupled Device) or CMOS (or Complementary Metal-Oxide-Semiconductor)).
  • the decoded SDR or HDR picture is sent to a destination; specifically, the destination belongs to a set comprising:
  • a local memory (1203 or 1204), e.g. a video memory or a RAM, a flash memory, a hard disk ;
  • a storage interface (1205) e.g. an interface with a mass storage, a RAM, a flash memory, a ROM, an optical disc or a magnetic support;
  • a communication interface (1205) e.g. a wireline interface (for example a bus interface (e.g. USB (or Universal Serial Bus)), a wide area network interface, a local area network interface, a HDMI (High Definition Multimedia Interface) interface) or a wireless interface (such as a IEEE 802.1 1 interface, WiFi ® or a Bluetooth ® interface); and
  • a wireline interface for example a bus interface (e.g. USB (or Universal Serial Bus)
  • a wide area network interface e.g. USB (or Universal Serial Bus)
  • a wide area network interface e.g. USB (or Universal Serial Bus)
  • a local area network interface e.g. HDMI (High Definition Multimedia Interface) interface
  • a wireless interface such as a IEEE 802.1 1 interface, WiFi ® or a Bluetooth ® interface
  • bitstream F1 , F2 and/or F3 are sent to a destination.
  • bitstreams F1 , F2 and F3 or both bitstreams are stored in a local or remote memory, e.g. a video memory (1204) or a RAM (1204), a hard disk (1203).
  • one or both bitstreams are sent to a storage interface (1205), e.g. an interface with a mass storage, a flash memory, ROM, an optical disc or a magnetic support and/or transmitted over a communication interface (1205), e.g. an interface to a point to point link, a communication bus, a point to multipoint link or a broadcast network.
  • the bitstream F1 , F2 and/or F3 is obtained from a source.
  • the bitstream is read from a local memory, e.g. a video memory (1204), a RAM (1204), a ROM (1203), a flash memory (1203) or a hard disk (1203).
  • the bitstream is received from a storage interface (1205), e.g. an interface with a mass storage, a RAM, a ROM, a flash memory, an optical disc or a magnetic support and/or received from a communication interface (1205), e.g. an interface to a point to point link, a bus, a point to multipoint link or a broadcast network.
  • device 1200 being configured to implement an encoding method described in relation with one of the Figs. 2, 4-8d, 10a-c, belongs to a set comprising:
  • a video server e.g. a broadcast server, a video-on-demand server or a web server.
  • device 1200 being configured to implement a decoding method described in relation with one of the Figs. 3, 9 11a-d, belongs to a set comprising:
  • the device A comprises a processor in relation with memory RAM and ROM which are configured to implement a method for encoding a picture as described in relation with one of the Figs. 2, 4-8d, 10a-c
  • the device B comprises a processor in relation with memory RAM and ROM which are configured to implement which are configured to implement a method for decoding as described in relation with one of the Figs. 3, 9 11a-d.
  • the network is a broadcast network, adapted to broadcast still pictures or video pictures from device A to decoding devices including the device B.
  • Implementations of the various processes and features described herein may be embodied in a variety of different equipment or applications.
  • Examples of such equipment include an encoder, a decoder, a post- processor processing output from a decoder, a pre-processor providing input to an encoder, a video coder, a video decoder, a video codec, a web server, a set-top box, a laptop, a personal computer, a cell phone, a PDA, and any other device for processing a picture or a video or other communication devices.
  • the equipment may be mobile and even installed in a mobile vehicle.
  • a computer readable storage medium can take the form of a computer readable program product embodied in one or more computer readable medium(s) and having computer readable program code embodied thereon that is executable by a computer.
  • a computer readable storage medium as used herein is considered a non -transitory storage medium given the inherent capability to store the information therein as well as the inherent capability to provide retrieval of the information therefrom.
  • a computer readable storage medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. It is to be appreciated that the following, while providing more specific examples of computer readable storage mediums to which the present principles can be applied, is merely an illustrative and not exhaustive listing as is readily appreciated by one of ordinary skill in the art: a portable computer diskette; a hard disk; a read-only memory (ROM); an erasable programmable read-only memory (EPROM or Flash memory); a portable compact disc read-only memory (CD-ROM); an optical storage device; a magnetic storage device; or any suitable combination of the foregoing.
  • the instructions may form an application program tangibly embodied on a processor-readable medium.
  • Instructions may be, for example, in hardware, firmware, software, or a combination. Instructions may be found in, for example, an operating system, a separate application, or a combination of the two.
  • a processor may be characterized, therefore, as, for example, both a device configured to carry out a process and a device that includes a processor-readable medium (such as a storage device) having instructions for carrying out a process. Further, a processor-readable medium may store, in addition to or in lieu of instructions, data values produced by an implementation.
  • implementations may produce a variety of signals formatted to carry information that may be, for example, stored or transmitted.
  • the information may include, for example, instructions for performing a method, or data produced by one of the described implementations.
  • a signal may be formatted to carry as data the rules for writing or reading the syntax of a described embodiment, or to carry as data the actual syntax-values written by a described embodiment.
  • Such a signal may be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal.
  • the formatting may include, for example, encoding a data stream and modulating a carrier with the encoded data stream.
  • the information that the signal carries may be, for example, analog or digital information.
  • the signal may be transmitted over a variety of different wired or wireless links, as is known.
  • the signal may be stored on a processor-readable medium.

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Abstract

La présente invention concerne un procédé et un dispositif pour coder à la fois une image HDR (IHDR) et une première image SDR (ISDR1) obtenue à partir de ladite image HDR, dans au moins un train de bits (F1, F2, F3, F4). Le procédé comprend : - l'obtention (210) d'une deuxième image HDR (ISDR2) par mappage de tons de l'image HDR (IHDR); - l'obtention (230) d'une fonction de mappage de couleurs (CMF) qui permet le mappage des couleurs de la deuxième image SDR (ISDR2) sur les couleurs d'une troisième image SDR (ISDR3) obtenue (220) à partir de la première image SDR (ISDR1); - le codage (240), dans un train de bits, d'une information (INF) représentative de la fonction de mappage de couleurs; et - le codage (260), dans un train de bits, d'une quatrième image SDR (ISDR4) obtenue (250) à partir de la première image SDR (ISDR1). La présente invention concerne en outre un procédé et un dispositif de décodage.
EP16775474.6A 2015-06-30 2016-06-27 Procédé et dispositif pour coder à la fois une image hdr et une image sdr obtenue à partir de ladite image hdr à l'aide de fonctions de mappage de couleurs Pending EP3318063A1 (fr)

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PCT/EP2016/064837 WO2017001330A1 (fr) 2015-06-30 2016-06-27 Procédé et dispositif pour coder à la fois une image hdr et une image sdr obtenue à partir de ladite image hdr à l'aide de fonctions de mappage de couleurs

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CN114189691A (zh) 2022-03-15
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EP3113496A1 (fr) 2017-01-04
TWI763629B (zh) 2022-05-11
JP2018524924A (ja) 2018-08-30
KR102367205B1 (ko) 2022-02-23
TW201701658A (zh) 2017-01-01
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KR20180021747A (ko) 2018-03-05
US20180192077A1 (en) 2018-07-05

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